The parents heard news on the radio of a shooting near UC Santa Barbara as they were driving on the 101 Freeway

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A man who identified himself as Elliot Rodger appears in a video posted to YouTube.

The parents of a man who went on a killing spree in Isla Vista rushed to the college town as the rampage began after discovering the troubling manifesto outlining their son's plans, a family friend confirmed to NBC News.

Just after 9:17 p.m. Friday, the mother of suspected gunman Elliot Rodger saw the 100-plus-page document railing against women and detailing his plans to go on a killing spree, said family friend Simon Astaire, who is a talent agent and media adviser.

After seeing the document and a YouTube video titled "Retribution," in which Rodger vowed to get "revenge against humanity," Rodger's mother, Chin Rodger, called her ex-husband and two decided to race to Isla Vista in search of their son, Astaire said. On the way there, they called authorities and agreed to meet when they arrived.

While driving up the the 101 Freeway toward Isla Vista, they heard news on the radio of a shooting near UC Santa Barbara, Astaire said. By the time the parents arrived, authorities had confirmed that the gunman was their son.

The gunfire broke out about 9:30 p.m. outside the Alpha Phi sorority house, where Rodger fatally shot two UCSB students, sheriff’s officials said. He went on to fire shots at multiple locations around the area, killing another student at a nearby deli.

Authorities say Rodger also stabbed three men to death inside his Isla Vista apartment before the shooting.

The killing spree ended when Rodger apparently took his own life during a car pursuit, officials said.

Published at 4:13 AM EDT on May 26, 2014 | Updated at 7:38 AM EDT on May 29, 2014